Shower Head wont fit on shower arm

I just purchased a new shower head for my shower and the arm of the shower does not seem to accept the shower head. It has a screw that is on the shower arm and somthing like a ball on the tip of the arm. Is there any other showerheads that any one knows that fit this type of shower arm? Or should I just replace the arm. Thanks

You have an old ball end arm, and it will only accept ONE shower head, made by that particular company. The two well-known ball end arms were Price Pfister, and American Standard ( and they have different threads from one another).

It is getting very difficult to find either of those heads. You should remove that arm and replace it